1. Field of the Invention
The present invention relates to an intra prediction mode selecting apparatus and a method thereof. More particularly, the present invention relates to an intra prediction mode selecting apparatus with a format of H.264 and a method thereof.
2. Description of Related Art
With development of the electronic technology, image display techniques are accordingly developed. Especially, regarding an animation image display, to effectively improve a performance of the animation image of a display device, a plurality of image compression standards is provided, wherein H.264 is a most representative high compression digital video coding and decoding standard.
According to the H.264 coding and decoding standard, when an intra prediction mode to be selected is determined, cost functions of all possible intra modes have to be first calculated. The intra prediction modes include four categories of an I4 macro-block mode, an I8 macro-block mode, an I16 macro-block mode and a chroma mode, and the four categories of the intra prediction modes further include 26 sub-modes to be calculated. Moreover, the so-called close loop predictions have to be performed to the I4 macro-block mode and the I8 macro-block mode. Therefore, determination of the intra prediction mode to be selected consumes considerable hardware resources and bandwidth used for calculation. Accordingly, scheduling of the I4 macro-block mode, the I8 macro-block mode, the I16 macro-block mode and the chroma mode during the prediction is quite important.
Referring to FIG. 1, FIG. 1 is a diagram illustrating a schedule method of a conventional intra prediction mode. As shown in FIG. 1, the predictions are sequentially performed in allusion to the I4 macro-block mode, the I16 macro-block mode and the chroma mode. In brief, predictions 111-112 of the I4 macro-block mode and reconstructions 121-122 of the I4 macro-block mode are sequentially performed in allusion to different blocks of a frame data. Then, predictions 131-132 of the I16 macro-block mode are sequentially performed in allusion to different blocks of the frame data. Finally, a prediction 141 of the chroma mode is performed. Referring to FIG. 2, FIG. 2 is a diagram illustrating an interlaced schedule method of a conventional intra prediction mode. Different to the schedule method of FIG. 1, predictions 231 and 232 of the I16 macro-block are respectively inserted in idle periods generated when reconstructions 221 and 222 of the I4 macro-block are performed. Thus, extra time for executing the predictions of the I16 macro-block can be effectively saved, so as to save a bandwidth of operation.
Since the I8 macro-block mode is not considered in both of the schedule methods of FIG. 1 and FIG. 2, another embodiment is provided below. FIG. 3 is a diagram illustrating a schedule method of a conventional high profile simplified intra prediction mode. According to the schedule method of FIG. 3, the I16 macro-block mode is neglected, and an open-loop operation (only the predictions of the I4 and I8 macro-block modes are performed, and the reconstructions thereof are not performed) is performed to reduce the required hardware resources and bandwidth.